Process for making iron and steel from smelter slags



Get. 16 E923. 1,4712% c. R. KUZELL PROCESS FOR MAKING IRON AND STEELFROM SMELTER SLAGS Filed Aug. 15, 1921 Patented @ct. is, rare.

CHARLES R. KUZELL, 0F CLARKDALE, ARIZONA.

PROCESS FOR MAKING IRON AND STEEL FROM SHELTER SLAGS.

Application .filed August 15, 1921. Serial No. 492,841.

To all whom it may concern:

Be it known that 1, CHARLES R. KUZ LL, a citizen of the United States,residing at (.larkdale, in the county of Yavapai and State of Arizona,have invented certain new and useful Improvements in Processes forMaking Iron and Steel from Smelter Slags, of which the following is aspecification,

My invention has relation to improvements in processes for making ironand steel from smelter slags, and consists in the novel features-morefully set forth in the specification and pointed out in the claims.

.In the smelting of copper for making matte, the slag contains a largepercentage of iron as oxide (i. e., wholly or partially combined withsilica as silicate of iron) which, under the prevailing practice, iswasted. Now, it is the object of the present invention to recover thisiron from the slag by reducing the oxide and converting the iron to castor pig iron, although if desirable the process also contemplates themanufacture of steel from the recovered iron. The advantages of theinvention will be better apparent from the following detaileddescription of the process, 111 connection with the drawing whichrepresents a longitudinal section of a modified form of converter.

The smelter slag is introduced into a crucible, converter or equivalentvessel while still molten. We will assume that an ordinary copperconverter is used, eX- cept that'instead of a single row of tuyeresthere are two rows, the one discharging below the surface of the bathwhen the converter is in blowing position, while the other willdischarge above the bath.

After the molten slag has been introduced into the converter C, it istilted back 7 capacity of air that is necessary to inject the to blowingposition and powdered coal, or powdered coal and flux (preferablypowdered lime rock) are introduced by a current of air through the lowerset of tuyeres 1 and into the bath. However, the amount of air thatenters with the fuel, or the fuel and flux, is so regulated as not to hesufficient for complete combustion of the fuel. This, obviously must bethe case, because the carbon in the fuel is brought into contact withthe iron oxide to effect a reduction thereof. The number and size of thelower row of tuyeres 1 are limited to the powdered coal, or coal andflux, into the bath, However, it is important that the amount of air bekept as low as possible so that complete combustion of the fuel does nottake place. duced by the coal it will be replaced in the slag by thelime, and the basic constituent of the slag thus kept at a balance so asnot' to reduce the fluidity thereof. The metallic iron will drop to thebottom of the bath and may be removed after skimming 0d the slag. As theiron is gradually replaced by the lime there is a tendency for the slagto thicken, and an increased temperature is required to maintain thenecessary fluidity to carry on the operation. For this purpose I providea second row of tuyeres 2, above the first row and adapted to dischargeair into the converter above the sur-' face of the bath. This airsupports the combustion of the volatile combustibles, such as CO, risingfrom the surface of the bath, during the reduction of the iron, andfurnishes additional heat, which is transmitted to the bath by radiationand conduction. The bath is thus kept fluid so that the reduction mayproceed practically to completion.

After the reduction has proceeded to the proper degree, the slag isskimmed ofi and the iron may beremoved for cast iron or pig iron.However, if desired, the iron may be left in the converter ortransferred i to an ordinary steel converter and blown to produce steel,as well understood in the art. While the coal and flux are preferablysupplied to the bath through the lower row of tuyeres 1, I do not wishto be restricted to this method as, obviously it. may be chargeddirectly through the mouth of the converter, or otherwise. Then again ifcharged through the mouth of the converter the fuel and flux need notnecessarily be powdered.

The use of the smelter slag while still molten as it comes from thesmelter furnaces results in the saving of heat in the molten slag. Afurther economy results from the use of coal to bring about thereduction, since coal is cheaper than coke used in standard iron blastfurnace practice. Then again the type of furnace in whichthe reductiontakes place will permit the making of steel in the same furnace ifdesired. I

In practicing the invention, the quantities As the iron oxide is reofthe reagents, the manner of charging them into the bath and manipulationthereof will be determined largely by the skilled metallurgist in chargeof the operation. The amount of fuel required may be reduced bypreheating the air if desired.

Having described'my invention, ll claim: 1. The' process ofmanufacturing iron from smelter slags which consists in subjecting acharge of molten slag to the action of a blast of air charged withpowdered Y carbonaceous. fuel directed into the bath of slag below thesurface thereof, continuing the blowing operation with an excess of fuelin the presence of suitable fluxing material permeating the bath, andprojecting above the bath a blast of a supporter of combustion.

2. The process of manufacturing iron from smelter slags which consistsin introduclng into the molten slag a reducing agent in the presence ofa fluxing material,

and projecting above the charge a blast of a supporter of combustion.

3. The process of manufacturing iron from smelter slags whichconsists insubjecting a charge of molten slag to a blast of .air carryingpowdered-coal, introducing a suitable fluxing material into the charge,and projecting above the charge a blast of a supporter of combustion.

4. The process of manufacturing iron from smelter slags, which consistsin charg- .coal reduces the iron in thecharge, and introducing asupporter of combustion above the charge.

6. The process of manufacturing iron from smelter slags which consistsin placing a charge of molten slag into a treatment vessel, introducingair and powdered coal into the charge to raise the temperature of thebath, the air being insufficient to complete the combustion of the coalwhich effects a. reduction of the iron in the charge. introducing into1118 charge lime to replace the iron in the charge and to form a limeslag, directing into the treatment vessel above the charge a supporterof combustion for raising the temperature of the bath.

and finally removing the iron.

In testimony whereof I hereunto afiix my signature.

CHARLES R. KUZELL.

